How do I get a breakdown by the hour using a single query in MySql? - mysql

Question

Let's say my table looks like this:
Sessions
start_dts (datetime)
end_dts (datetime)
and the data looks like this:
start_dts end_dts
12/25/2011 01:55:00 12/25/2011 03:30:00
I need the query results to look like this:
Date Hour MinutesOnline
12/25/2011 0 0
12/25/2011 1 5
12/25/2011 2 60
12/25/2011 3 30
... (every hour of the date range being queried)
Is this even possible with a single query?

Answer 1

Here is a pretty good start. This will work for any date/time range. However, it has one main prerequisite: You need to create an intervals table with a dt_hr datetime field which contains all the intervals you are scanning over.
Ex: '2011-12-25 00:00:00',
'2011-12-25 01:00:00',
'2011-12-25 02:00:00',
'2011-12-25 03:00:00',
. . .
'2011-12-25 23:00:00'
-
SELECT DATE_FORMAT(intervals.dt_hr,'%m/%d/%Y') AS Date,
EXTRACT(HOUR FROM intervals.dt_hr) AS Hour,
CASE
WHEN intervals.dt_hr > TIMESTAMPADD(HOUR,HOUR(s2.start_dts), DATE(s2.start_dts))
AND intervals.dt_hr < TIMESTAMPADD(HOUR,HOUR(s2.end_dts), DATE(s2.end_dts))
THEN 60
WHEN intervals.dt_hr = TIMESTAMPADD(HOUR,HOUR(s2.start_dts), DATE(s2.start_dts))
AND intervals.dt_hr < TIMESTAMPADD(HOUR,HOUR(s2.end_dts), DATE(s2.end_dts))
THEN 60 - EXTRACT(MINUTE FROM s2.start_dts)
WHEN intervals.dt_hr = TIMESTAMPADD(HOUR,HOUR(s2.end_dts), DATE(s2.end_dts))
AND intervals.dt_hr > TIMESTAMPADD(HOUR,HOUR(s2.start_dts), DATE(s2.start_dts))
THEN EXTRACT(MINUTE FROM s2.end_dts)
WHEN intervals.dt_hr = TIMESTAMPADD(HOUR,HOUR(s2.start_dts), DATE(s2.start_dts))
AND intervals.dt_hr = TIMESTAMPADD(HOUR,HOUR(s2.end_dts), DATE(s2.end_dts))
THEN EXTRACT(MINUTE FROM s2.end_dts) - EXTRACT(MINUTE FROM s2.start_dts)
ELSE 0
END AS MinutesOnLine
FROM intervals
LEFT JOIN sessions s2
ON intervals.dt_hr >= TIMESTAMPADD(HOUR,HOUR(s2.start_dts), DATE(s2.start_dts))
AND intervals.dt_hr <= TIMESTAMPADD(HOUR,HOUR(s2.end_dts), DATE(s2.end_dts))
To generate the intervals table, you could create a stored procedure which creates a temporary table with a date_hour sequence. See Get a list of dates between two dates for a way to do this.

Answer 2

More of a big comment than answer.
Not good enough with MySQL to do it but
a CTE to come up with a set of datetimes between start_dts and end_dts
so you get
startTime endTime
12/25/2011 01:00:00 12/25/2011 02:00:00
12/25/2011 02:00:00 12/25/2011 03:00:00
12/25/2011 03:00:00 12/25/2011 04:00:00
joined back to session On CT.EndTime < DateAdd(sessions.end_dts, INTERVAL 1 HOUR)
and then Hour(CTS.StartTime) - Hour(sessions.start_dts)
and modulus of the time difference in minutes beteen cte.endtime and start_dts
maybe...